Historically, providing uniform vapor distribution in fractionation towers, and in particular high capacity and large diameter fractionation towers, is one of the most challenging aspects of designing a high performance column. Examples include vapor distribution in the flash zone of a vacuum distillation unit (VDU) at oil refineries. For all towers, and especially for large diameter columns, it requires an innovative design for the vapor inlet device and internals. It will be recognized that such designs may also be used for a variety of other applications.
Several innovations have been made to address the problem of ensuring good mixing. Muller in U.S. Pat. No. 4,770,747 (1988) describes an inlet horn for feeding a vapor stream tangentially into an atmospheric or vacuum column so as to provide distribution of the inlet vapor stream and to provide separation of any entrained liquid in said stream. Vanes are used to deflect the vapor component of the stream in a controlled manner. Lee et al. in U.S. Pat. No. 5,106,544 (1992) describe a combination of an inlet horn having a 360 degree annular housing with directional flow vanes. Hsieh et al. in U.S. Pat. No. 5,605,654 (1997) describe a vapor distributor having an annular housing with a series of ports for feeding the vapor stream in a distributed manner. Laird et al. in U.S. Pat. No. 6,889,961 (2005) described a modified vapor distributor with baffles in the lower intermediate transitional section to reduce swirling of the feed and thereby improve distribution. Laird et al. in U.S. Pat. No. 6,889,962 (2005) describe an annular inlet vapor horn that circulates the inlet feed so as to de-entrain any liquid droplets while providing for more even distribution of the inlet flow across the column. Lee et al. in U.S. Pat. No. 6,948,705 (2005) describe a gas-liquid contacting apparatus in which a gas stream, for example steam, is fed into a column via an annular vapor horn. Laird et al. in U.S. Pat. No. 7,104,529 (2006) describe a vapor distributor apparatus, the vapor horn of which includes a series of vanes the sizes of which increase with distance from the inlet nozzle of the vapor distributor. In the majority of devices having a vapor horn, the inlet flow is uni-directional and has a cyclonic effect on the vapor feed. Baffles or vanes are used to redirect or disrupt the circular flow of the inlet stream. Yeoman et al. in U.S. Pat. No. 5,632,933 (1997) describe an annular bi-directional gas flow device having a plurality of outlets at an inner wall of the housing and a series of flow directing vanes for distribution of an inlet vapor stream across the breadth of a column.